* {
    text-align: center;
    line-height: 1.25;
    letter-spacing: 2px;
    word-spacing: 4px;
}
table {
    table-layout: fixed;
    width: 400px;
    border-collapse: collapse;
    margin: auto;
    background: yellowgreen;
}
tr,th {
    border: 1px solid;
    font-size: 16px;
    font-weight: normal;
    text-align: center;
}
.advance {
    list-style: square;
    text-decoration: underline;
    text-align:left;
    color: red;
}
p {
    font-family: "Arail";
}
h1 {
    /* 水平偏移 垂直偏移 模糊半径 */
    text-shadow: 2px 2px 5px;
}
.disadvance {
    text-decoration: line-through;
    color: green
}
.disadvance > li {
    list-style: none;
    background: url('./img/叉.png') no-repeat 0rem 0.3rem;
    background-size: 1rem 1rem;
    background-position: 47%;
    text-indent: 1.5em;
    text-align: center;
}
.advance > li {
    list-style: none;
    background: url('./img/勾选.png') no-repeat 0rem 0.3rem;
    background-size: 1.2rem 1.2rem;
    background-position: 47%;
    text-indent: 1.5em;
    text-align: center;
}
.introduction  {
    background-image: url("./img/1.jpg");
    background-repeat: no-repeat;
    /* 相对位置% 关键字top left right top bottom center */
    background-position: 70% 80%;
    background-size: 10%;
}

h3 {
    /* border: 1px dotted; */
    border-width: 1px;
    border-style: solid dotted;
    border-color: gray;
}

/* div > p {
    text-align: center;
    width: 400px;
    border-style: solid none solid none; 
    border-width: 1px;
} */

a:link {
    color: #3f3f3f;
    text-decoration: none;
}

a:visited {
    color: orange;
    text-decoration-line: line-through;
}

a:hover {
    color: blue;
    text-decoration-line: underline;
}

a:active {
    color: red;
}